GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: AncientSword on January 25, 2013, 09:49:10 AM
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I did a search, but can't find anything. Do any of you know the twist rate of the stock Marauder .25 barrel? I just put a ballistic app on my Android phone and I am trying to plug in all the correct variables.
While I am at it, anyone know the approximate BC of a pellet? :)
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I did a search, but can't find anything. Do any of you know the twist rate of the stock Marauder .25 barrel? I just put a ballistic app on my Android phone and I am trying to plug in all the correct variables.
While I am at it, anyone know the approximate BC of a pellet? :)
I don't know the twist right now but I'll check the next time a clean the barrel.
(easy to do really)
1. Remove the shroud and measure the barrel length from breech to muzzle
2. Remove the bolt like you are cleaning the barrel
3. Put a white (on any color) dot on the top of your cleaning rod in paint (a dot)
4. Place the rod with tight patch into breech and watch the mark turn (stop as soon as you get one complete revolution.
5. Mark your rod right at the breech when it makes one complete turn,( so there will be two marks top dead center on your rod X amount of inches apart.
6. Push the rod the rest of the way through, pull the rod out and measure the length between marks and you have your twist rate.
1 complete turn in X number of inches.
I suspect it's something like 1:16"
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Ballistic coefficients are a variable for a reason...they vary. :) They vary from gun to gun and with atmosheric conditions. The newest version of chairgun has several popular pellets BC already.
The best way to find the BC of a pellet in your gun in your shooting environment is to figure them. Chairgun has a calculator function for this using pellet drop vs distance or speed variance vs distance. If nohting else it is a good excuse to go shoot.
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The BC of a pellet also varies in one given rifle as you change the velocity.... Wadcutters start out poor and get worse as you increase the velocity.... Domed start out good, get better, and then fall off again.... There is no substitute to taking your own measurements if you really want an accurate BC for a given pellet in a given circumstance.... The numbers in ChairGun are really only a guide....
Bob
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Twist rate is 1-18" . Triple checked just now.
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Thanks for the info guys. I do remember reading that the BC changes with velocity. I thought that sometimes, if the changes are minor that it didnt matter much. I guess I am just looking for ballpark numbers, as I will do my own testing in time.
On the barrel twist, is it right or left hand twist?